Coloring metal pigment and resin composition containing the coloring metal pigment

ABSTRACT

In order to provide a color metallic pigment capable of implementing diverse colors, excellent in finished appearance and weather resistance and manufacturable by a safe and simple manufacturing method, a color metallic pigment comprising metal particles and a single-layer or multilayer coat covering the surface of each metal particle characterized in that at least one layer of the single-layer or multilayer coat is a cobalt coat consisting of an anhydrous oxide film elementally containing cobalt is provided. This cobalt coat preferably contains a compound in composition expressed by at least one type of composition selected from a group consisting of CoO, Co 2 O 3 , Co 3 O 4 , nCoO.mAl 2 O 3  and nCoO.mSiO 2  (n, m: arbitrary positive real numbers).

TECHNICAL FIELD

The present invention relates to a color metallic pigment. Morespecifically, the present invention relates to a color metallic pigmentcomprising a single-layer or multilayer coat. The present invention alsorelates to a resin composition containing the aforementioned colormetallic pigment.

BACKGROUND TECHNIQUE

A film formed with a metallic paint reflects external incident lightwith a flaky metallic pigment contained in the film, for exhibiting aglittery design. The reflection of light presents a unique appearanceexcellent in design along with each color tone of the film.

With such characteristics, a metallic pigment mainly employing aluminumflakes as basic particles is applied to a metallic design for automobilepaint finish, plastic paint finish, printing ink or a resin compositionmolding.

In recent years, a colorful and highly bright metallic pigment coloredred, green, purple or the like has been desired followingdiversification of consumers' preference. However, the originallyachromatic aluminum flakes forming a pigment presenting silver-grayluster cannot satisfy the aforementioned consumers' demand as such.

Therefore, many attempts have been made in order to solve these problemsand satisfy the consumers' requirement for diverse colors. For example,Japanese Patent Laying-Open No. 58-141248, National Patent PublicationNo. 5-508424, Japanese Patent Laying-Open No. 1-315470, Japanese PatentLaying-Open No. 9-40885, Japanese Patent Laying-Open No. 9-59532 orJapanese Patent Laying-Open No. 9-124973 discloses a technique relatedto a color metallic pigment prepared by bonding a color pigment to metalparticles.

A method of bonding a color pigment to the surfaces of metal particlesand covering the same with coats consisting of a polymer composition isgenerally employed as a method of preparing such a color metallicpigment. Further, an organic pigment such as adiketopyrrolopyrrole-based, quinacridone-based, dioxazine-based,isoindolinone-based, condensed azo-based, threne-based, perinone-based,perylene-based, phthalone-based or phthalocyanine-based pigment or aninorganic pigment such as iron oxide or carbon black is generally usedas the color pigment employed for such a color metallic pigment.

In this color metallic pigment, however, the color pigment bonded to thesurfaces of the metal particles is disadvantageously easy tophoto-deteriorate due to reflection of light on these surfaces. Apigment such as phthalocyanine green, phthalocyanine blue or iron oxiderelatively excellent in light fastness must be selected in order tosolve this problem, and hence the design of the obtained color metallicpigment is limited under the present circumstances.

On the other hand, Japanese Patent Laying-Open No. 63-161063, JapanesePatent Laying-Open No. 4-28771 or Japanese Patent Laying-Open No.2001-316609 discloses a technique of forming a film of silicon oxide,titanium oxide or metal on the surface of a pearlescent pigment such asmica thereby providing a colored nacreous pigment provided with aninterference color. However, the hiding power of this colored nacreouspigment is so small that the pigment cannot sufficiently conceal theground when compounded with a paint or ink.

With respect to these problems, some techniques have been disclosed inrelation to a color metallic pigment obtained by coating the surfaces ofmetal particles having high hiding power with interference films ofsilicon oxide, aluminum oxide or titanium oxide.

For example, Japanese Patent Laying-Open No. 1-110568 or Japanese PatentLaying-Open No. 2-669 discloses a method of depositing titanium oxide onthe surfaces of metal particles by a sol-gel method. According to thismethod, however, no color metallic pigment having high chroma can beobtained but the titanium oxide layers must be in an active anatasephase, to disadvantageously prompt deterioration of resin and reduceweather resistance when compounded with a paint or the like.

Japanese Patent Laying-Open No. 56-120771, Japanese Patent Laying-OpenNo. 1-311176 or Japanese Patent Laying-Open No. 6-32994 discloses amethod of obtaining a composite phase of iron oxide, titanium oxide ormetallic oxide and carbon, metal or metallic oxide on the surfaces ofmetal particles by a gas phase method. When employing the gas phasemethod, however, it is necessary to fluidize the metal particles andsupply a precursor of metallic oxide for heating/depositing the same,while a specific apparatus is required, the metal particles areremarkably in danger of dust explosion, and the precursor of themetallic oxide is generally hard to handle due to strong toxicity.

Japanese Patent Laying-Open No. 8-209024 discloses a technique relatedto a multilayer coat metallic pigment based on a two-layer structure ofa colorless cover layer having a refractive index of not more than 1.8and a selective absorption layer having a refractive index of at least2.0. However, while this technique discloses a method of formingmetallic oxide layers on the surfaces of metal particles by the gasphase method or a method of hydrolyzing a metallic compound in asolution, the gas phase method has the aforementioned disadvantage, andthe hydrolytic reaction is caused in a basic or acidic atmospherecontaining a large quantity of water in the method of hydrolyzing themetallic compound in the solution for forming the metal oxide layers andhence the metal particles may react with the water during a treatmentstep to disadvantageously result in agglomeration of the metal particlesor acceleration of the reaction.

Japanese Patent laying-Open No. 51-150532 or Japanese Patent Laying-OpenNo. 63-15861 discloses a method of mixing aluminum powder, metallic saltand a chelate compound with each other for depositing a metallic oxidelayer. However, the method described in Japanese Patent Laying-Open No.51-150532, carried out in an aqueous solution with the aluminum powderremarkably in danger of strongly reacting with the solution for thetreatment, may unpractically cause a problem such as generation of alarge quantity of hydrogen gas, remarkable heat generation resultingfrom acceleration of reaction or agglomeration of the aluminum powder.

Also in the method described in Japanese Patent Laying-Open No.63-15861, it is difficult to avoid the aforementioned problem resultingfrom strong reaction between the aluminum powder and the solution forthe treatment, while the reaction is caused in an acidic to neutralregion and hence deposition of the metallic compound is not efficientlyperformed but unreacted metallic salt disadvantageously remains in alarge quantity.

The metallic oxide layer obtained by this method, formed by a hydratedfilm containing water, is inferior in adhesiveness to a binder such asresin contained in the paint and tends to cause a problem such aspeeling or reduction of moisture resistance with time. Further, the filmof the aforementioned metallic oxide layer formed by the hydrated filmtends to be incomplete, and disadvantageously exhibits rather inferiorcolor development in general.

DISCLOSURE OF THE INVENTION

While development of a color metallic pigment capable of implementingdiverse colors, excellent in finished appearance and weather resistanceand manufacturable by a safe and simple manufacturing method is stronglydemanded as hereinabove described, a technique related to such a colormetallic pigment is still unknown.

On the basis of the aforementioned circumstances, an object of thepresent invention is to provide a color metallic pigment capable ofimplementing diverse colors, excellent in finished appearance andweather resistance and manufacturable by a safe and simple manufacturingmethod.

Another object of the present invention is to provide a resincomposition capable of implementing diverse colors, excellent infinished appearance and weather resistance and manufacturable by a safeand simple manufacturing method.

The inventors have obtained such an idea that light interference may beutilized for attaining the aforementioned objects by providing asingle-layer or multilayer coat containing dissimilar metallic elementson the surface of a metal particle forming each base particle by a safeand simple method, and made deep study as to various types of metallicelements.

As a result of trial and error, the inventors have found out that ananhydrous oxide film elementally containing cobalt can be safely andsimply provided on the metal particle forming each base particle whenemploying a specific manufacturing method so that a color metallicpigment having an excellent appearance can be obtained as a result.

The inventors have also found out that an oxide film or an oxynitridefilm containing dissimilar metallic elements such as titanium can befurther safely and simply provided outside the aforementioned anhydrousoxide film elementally containing cobalt when employing a specificmanufacturing method so that a color metallic pigment having morediverse colors can be obtained.

The inventors have found out that a coat elementally containingaluminum, silicon or cerium can be safely and simply provided outsidethe oxide film or the oxynitride film containing titanium when employinga specific manufacturing method so that the problem of weatherresistance caused in the oxide film or the oxynitride film elementallycontaining titanium can be overcome, to complete the present invention.

The color metallic pigment according to the present invention is a colormetallic pigment comprising metal particles and a single-layer ormultilayer coat covering the surface of each metal particle, while atleast one layer of the single-layer or multilayer coat is a cobalt coatconsisting of an anhydrous oxide film elementally containing cobalt.

This cobalt coat preferably contains a compound in composition expressedby at least one type of composition selected from a group consisting ofCoO, Co₂O₃, Co₃O₄, nCoO.mAl₂O₃ and nCoO.mSiO₂ (n, m: arbitrary positivereal numbers).

This cobalt coat preferably has a thickness in the range of 0.01 to 1μm. Further, it is recommended that this cobalt element is contained inthe cobalt coat in the range of 0.5 to 50 parts by mass with respect to100 parts by mass of the metal particles.

The color metallic pigment according to the present invention preferablycomprises a silicon-aluminum coat consisting of an oxide filmelementally containing silicon and/or aluminum inside this cobalt coat.

This silicon-aluminum coat preferably contains a compound in compositionexpressed by at least one type of composition selected from a groupconsisting of Al₂O₃, SiO₂, SiO and nSiO₂.mAl₂O₃ (n, m: arbitrarypositive real numbers).

It is recommended that this silicon-aluminum coat has a thickness in therange of 0.01 to 1 μm. Further, this silicon and/or aluminum ispreferably elementally contained in the silicon-aluminum coat in therange of 0.01 to 50 parts by mass with respect to 100 parts by mass ofthe metal particles.

The color metallic pigment according to the present invention preferablycomprises a molybdenum-phosphorus coat consisting of an oxide filmelementally containing molybdenum and/or phosphorus on the surface ofeach metal particle.

It is recommended that this molybdenum-phosphorus coat contains acompound in composition expressed by at least one type of compositionselected from a group consisting of MoO₃, Mo₂O₃, MoO, nAl₂O₃.mMoO₃,nAl₂O₃.mMo₂O₃, nAl₂O₃.mMoO, P₂O₅ and nAl₂O₃.mP₂O₅ (n, m: arbitrarypositive real numbers).

This molybdenum and/or phosphorus is preferably elementally contained inthe molybdenum-phosphorus coat in the range of 0.01 to 5.0 parts by masswith respect to 100 parts by mass of the metal particles.

It is recommended that the color metallic pigment according to thepresent invention comprises a second coat consisting of an oxide film oran oxynitride film containing at least one element selected from a groupconsisting of titanium, zirconium, zinc, iron, chromium and ceriumoutside this cobalt coat.

This second coat preferably consists of an oxide layer or an oxynitridefilm elementally containing titanium. This second coat preferablycontains a compound in composition expressed by at least one type ofcomposition selected from a group consisting of rutile, anatase, TiO,Ti₂O₃ and Ti₃O₅.

Further, it is recommended that this second coat has a thickness in therange of 0.01 to 1 μm. In addition, at least one element selected fromthis group consisting of titanium, zirconium, zinc, iron, chromium andcerium is preferably contained in the second coat in the range of 0.5 to200 parts by mass with respect to 100 parts by mass of the metalparticles.

The color metallic pigment according to the present invention preferablycomprises a weather-resistant coat consisting of an oxide filmcontaining at least one element selected from a group consisting ofaluminum, silicon and cerium outside this second coat.

It is recommended that this weather-resistant coat contains a compoundin composition expressed by at least one type of composition selectedfrom a group consisting of Al₂O₃, SiO₂, SiO, CeO₂ and Ce₂O₃.

This weather-resistant coat preferably has a thickness in the rage of0.01 to 0.1 μm. Further, at least one element selected from this groupconsisting of aluminum, silicon and cerium is preferably contained inthe weather-resistant coat in the range of 0.01 to 5 parts by mass withrespect to 100 parts by mass of the metal particles.

It is recommended that the metal particles employed for the colormetallic pigment according to the present invention are flaky metalparticles made of aluminum or an aluminum alloy.

Further, the present invention includes a resin composition containingthe aforementioned color metallic pigment and resin.

BEST MODES FOR CARRYING OUT THE INVENTION

The present invention is now described in more detail with reference toan embodiment.

Color Metallic Pigment

The color metallic pigment according to the present invention is a colormetallic pigment comprising metal particles and a single-layer ormultilayer coat covering the surface of each metal particle, and atleast one layer of the single-layer or multilayer coat is a cobalt coatconsisting of an anhydrous oxide film elementally containing cobalt.

Metal Particle

The color metallic pigment according to the present invention comprisesthe metal particles as base particles.

The material for the metal particles forming the base particles of thecolor metallic pigment according to the present invention is notparticularly restricted but aluminum, copper, zinc, titanium, iron,nickel, chromium or an alloy thereof can be preferably employed as thematerial. Among these materials, aluminum or an aluminum alloy,excellent in metallic luster and hiding power, low-priced and easy tohandle due to small specific gravity, is particularly preferable.

While the shape of the metal particles employed for the presentinvention is not particularly restricted but can be selected fromvarious shapes such as granular, platelike, aggregated and flaky (scaly)shapes, the metal particles are preferably flaky in order to supplyexcellent brightness to a film.

When the metal particles employed for the present invention are flaky,the average thickness of these metal particles is preferably at least0.01 μm, more preferably at least 0.02 μm in particular. Further, theaverage thickness of these metal particles is preferably not more than 5μm, more preferably not more than 2 μm in particular. Metal particles ofless than 0.01 μm in average thickness are not industrially stablysupplied and tend to be hard to obtain, while metal particles exceeding5 μm in average thickness are not industrially stably supplied eitherand similarly tend to be hard to obtain.

When the metal particles employed for the present invention are flaky,the average particle diameter of these metal particles is preferably atleast 2 μm, more preferably at least 5 μm in particular. Further, theaverage particle diameter of these metal particles is preferably notmore than 300 μm, more preferably not more than 100 μm in particular.Metal particles of less than 2 μm in average particle diameter are notindustrially stably supplied and tend to be hard to obtain, while metalparticles exceeding 300 μm in average particle diameter are notindustrially stably supplied either and similarly tend to be hard toobtain.

When the metal particles employed for the present invention are flaky,further, a shape factor obtained by dividing the average particlediameter of these metal particles by the average thickness is preferablyat least 5, more preferably at least 50 in particular. Further, thisshape factor is preferably not more than 1000, more preferably not morethan 500 in particular. The metallic effect or the hiding property tendsto lower if this shape factor is less than 5, while deformation orbreaking tends to increase in a step of dispersion into a resincomposition if this shape factor exceeds 1000.

When the metal particles employed for the present invention are flaky,in addition, the shape of each metal particle is more preferably acoin-like shape with a smooth surface having a rounded end surface dueto clearness of an interference color.

When the metal particles employed for the present invention are flaky, amethod of grinding powder or metal flakes obtained by atomization by wetball milling (a.k.a. Hall process) or dry ball milling is preferable asthe method of manufacturing the flaky metal particles. Alternatively, amethod of forming a vacuum metallized thin film to a film consisting ofa resin composition or the like, thereafter separating the same anddisintegrating the same by the aforementioned disintegration method isalso employable.

The average particle diameter of the metal particles employed for thepresent invention or the color metallic pigment described later isobtained by calculating the volume average from particle sizedistribution measured by a known particle size distribution measuringmethod such as laser diffraction, micromesh sieving or coulter counting.The average thickness is calculated from the hiding power and thedensity of the metal particles or the color metallic pigment.

No grinding aid added in grinding is preferably adsorbed to the surfacesof the metal particles employed for the present invention.

Cobalt Coat

The color metallic pigment according to the present invention is a colormetallic pigment comprising metal particles and a single-layer ormultilayer coat covering the surface of each metal particle, and atleast one layer of the single-layer or multilayer coat is a cobalt coatconsisting of an anhydrous oxide film elementally containing cobalt.

When the cobalt coat consisting of the anhydrous oxide film elementallycontaining cobalt is formed outside each metal particle, the metalparticles can be colored green, yellow, brown etc., for obtaining thecolor metallic pigment according to the present invention.

A compound having composition such as CoO, Co₂O₃, Co₃O₄, nCoO.mAl₂O₃ ornCoO.mSiO₂ (n, m: arbitrary positive numbers) can be listed as aspecific example of a compound contained in this cobalt coat. Thiscobalt coat may contain a small quantity of metallic cobalt in a rangenot damaging optical transmission of the cobalt coat.

The thickness of this cobalt coat is preferably at least 0.01 μm, morepreferably at least 0.05 μm in particular. Further, this thickness ispreferably not more than 1 μm, more preferably not more than 0.8 μm inparticular. The color metallic pigment may exhibit no desired color ifthis thickness is less than 0.01 μm, while the luster of the colormetallic pigment tends to lower if this thickness exceeds 1 μm.

The quantity of the cobalt element contained in this cobalt coat ispreferably at least 0.5 parts by mass with respect to 100 parts by massof the metal particles forming the base particles, more preferably atleast 1 part by mass in particular. Further, the quantity of this cobaltelement is preferably not more than 50 parts by mass, more preferablynot more than 30 parts by mass in particular. There is a tendency thatno color metallic pigment of a desired color is obtained if the quantityof this cobalt element is less than 0.5 parts by mass, while the lusterof the color metallic pigment tends to lower if the quantity of thiscobalt element exceeds 50 parts by mass.

Cobalt Coat Forming Step

While a method of forming the cobalt coat consisting of the anhydrousoxide film containing the cobalt element outside each metal particleemployed as the base particle for the color metallic pigment accordingto the present invention is not particularly restricted, a method ofadding a cobalt compound to a suspension prepared by suspending themetal particles or the metal particles each already covered with thesingle-layer or multilayer coat in a hydrophilic solvent and stirring orkneading the slurried or pasty suspension while keeping this suspensionbasic thereby forming a hydrated film containing the cobalt elementoutside each metal particle and thereafter converting this hydrated filmto an anhydrous oxide film by heating or the like can be listed, forexample. According to this method, the hydrated film is converted to theanhydrous oxide film due to heat treatment, whereby a color metallicpigment excellent in color development is obtained and adhesivenessbetween the color metallic pigment according to the present inventionand binder resin contained in a paint is advantageously improved.

While the cobalt compound employed in the aforementioned method is notparticularly restricted, cobalt nitrate, cobalt acetate, cobaltphosphate, cobalt chloride, cobalt sulfate, cobalt naphthenate, cobaltoxalate, cobalt citrate, cobalt 2-ethylhexanoate, cobalt gluconate,cobalt chromate or cobalt carbonate can be listed, for example. Amongthese cobalt compounds, particularly preferable compounds are cobaltnitrate, cobalt acetate and cobalt chloride.

Further, while the hydrophilic solvent employed for the suspension isnot particularly restricted in the aforementioned case, methyl alcohol,ethyl alcohol, isopropyl alcohol, n-propyl alcohol, t-butyl alcohol,n-butyl alcohol, isobutyl alcohol, ethyl cellosolve, butyl cellosolve,propylene glycol monobutyl ether, dipropylene glycol monomethyl ether,propylene glycol monopropyl ether or acetone can be listed, for example.The aforementioned suspension may contain water.

In the aforementioned method, it is particularly preferable to add anamino compound to a suspension prepared by suspending the metalparticles or the metal particles each already covered with thesingle-layer or multilayer coat, adsorbing this amino compound to thesurface of the metal particle or the metal particle already covered withthe single-layer or multilayer coat while keeping the pH in the basicrange, thereafter add an aqueous solution prepared by dissolving thecobalt compound and perform heating/stirring thereby depositing a cobalthydrated film or the cobalt compound on the surface of the metalparticle or the metal particle already covered with the single-layer ormultilayer coat for finally heat-treating the same at a hightemperature. It is recommended to previously solid-liquid separate pastecontaining the metal particles each having the hydrated film from theaforementioned suspension before the final heat treatment.

While the amino compound employed for adjusting the pH of the suspensionin the aforementioned case is not particularly restricted,monoethanolamine, diethanolamine, triethanolamine, ammonia,ethylenediamine, t-butylamine, γ-aminopropyl triethoxysilane,N-2-aminoethyl-3-aminopropyl triethoxysilane,N-2-aminoethyl-3-aminopropylmethyl dimethoxysilane, urea orO-aminobenzoic acid can be listed, for example.

When keeping the pH in the basic range by adding the amino compound inthe aforementioned case, the kept pH is preferably at least 7.0, morepreferably at least 8.0 in particular. Further, this pH is preferablynot more than 14.0, more preferably not more than 10.0 in particular.Deposition of the cobalt compound may be insufficiently caused if thispH is less than 7.0, while it is generally difficult to adjust this pHto a value exceeding 14.0.

When adding the aqueous solution prepared by dissolving the cobaltcompound and performing heating/stirring in the aforementioned case, thetemperature of the suspension is preferably at least 20° C., morepreferably at least 50° C. in particular. Further, this temperature ispreferably not more than 120° C., particularly preferably not more than100° C. The cobalt compound tends to be incompletely deposited if thistemperature is less than 20° C., while the cobalt compound tends toprecipitate on a portion other than the surface of each basic metalparticle if this temperature exceeds 120° C.

When adding the aqueous solution prepared by dissolving the cobaltcompound and performing heating/stirring in the aforementioned case,further, the time for heating/stirring is preferably at least 5 minutes,more preferably at least 30 minutes in particular. Further, this time ispreferably not more than 10 hours, particularly preferably not more than3 hours. The cobalt compound tends to be incompletely deposited if thistime is less than 5 minutes, while deposition of the cobalt compoundtends not to further progress to result in economic disadvantage if thistime exceeds 10 hours.

When finally performing heat treatment at a high temperature aftersolid-liquid separation in the aforementioned case, the temperature forthe heat treatment is preferably at least 250° C., more preferably atleast 350° C. in particular. Further, this temperature is preferably notmore than 700° C., particularly preferably not more than 650° C. Colordevelopment tends to deteriorate due to insufficient vaporization ofwater of crystallization if this temperature is less than 250° C., whileagglomeration of the metal particles tends to easily occur if thistemperature exceeds 700° C.

When finally performing heat treatment at a high temperature in theaforementioned case, the time for the heat treatment is preferably atleast 30 minutes, more preferably at least 1 hour in particular.Further, this time is preferably not more than 20 hours, particularlypreferably not more than 10 hours. Color development of the colormetallic pigment tends to deteriorate if this time is less than 30minutes, while the color tone of the obtained color metallic pigmenttends to darken if this time exceeds 20 hours.

Silicon-Aluminum Coat

The color metallic pigment according to the present invention preferablycomprises a silicon-aluminum coat consisting of an oxide filmelementally containing silicon and/or aluminum inside the cobalt coat.

When the silicon-aluminum coat consisting of the oxide film elementallycontaining silicon and/or aluminum is provided inside the cobalt coat,the coloring effect with the cobalt coat is enhanced while an effect ofpreventing reducing reaction of the oxide in the cobalt coat with eachmetal particle is attained.

A compound having composition such as Al₂O₃, SiO₂, SiO or nSiO₂.mAl₂O₃(n, m: arbitrary positive real numbers) can be listed as a specificexample of the compound elementally containing silicon and/or aluminumcontained in this silicon-aluminum coat.

The thickness of this silicon-aluminum coat is preferably at least 0.01μm, more preferably at least 0.05 μm in particular. Further, thisthickness is preferably not more than 1 μm, more preferably not morethan 0.5 μm in particular. The color tone of the obtained color metallicpigment tends to darken if this thickness is less than 0.01 μm, whilethe luster of the color metallic pigment tends to lower if thisthickness exceeds 1 μm.

The elemental quantity of silicon and/or aluminum contained in thissilicon-aluminum coat is preferably at least 0.01 parts by mass withrespect to 100 parts by mass of the metal particles forming the baseparticles, more preferably at least 0.2 parts by mass in particular.Further, this quantity is preferably not more than 50 parts by mass,more preferably not more than 20 parts by mass in particular. The colortone of the obtained color metallic pigment tends to darken if thisquantity is less than 0.01 parts by mass, while the luster of the colormetallic pigment tends to lower if this quantity exceeds 50 parts bymass.

Silicon-Aluminum Coat Forming Step

While a method of forming the silicon-aluminum coat consisting of theoxide film elementally containing silicon and/or aluminum inside thecobalt coat provided on the color metallic pigment according to thepresent invention is not particularly restricted, a method of adding asilicon compound and/or an aluminum compound to a slurried or pastysuspension prepared by suspending the metal particles or the metalparticles each already covered with the single-layer or multilayer coatin a hydrophilic solvent, performing stirring or kneading while keepingthe pH of the suspension basic or acidic thereby forming a hydrated filmelementally containing silicon and/or aluminum on the surface of themetal particle or the metal particle already covered with thesingle-layer or multilayer coat for finally performing heat treatment ata high temperature and converting the hydrated film to an oxide film ispreferable, for example. It is recommended to previously solid-liquidseparate the paste containing the metal particles having the hydratedfilm from the aforementioned suspension before the final heat treatment.

While the silicon compound and/or the aluminum compound employed in theaforementioned method is not particularly restricted, methyltriethoxysilane, methyl trimethoxysilane, tetraethoxysilane,tetramethoxysilane or tetraisopropoxysilane, a condensate thereof,γ-aminopropyl triethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, N-2-aminoethyl-3-aminopropyl methyldimethoxysilane,sodium silicate, silicotungstic acid, silicomolybdic acid,triethoxyaluminum, trimethoxyaluminum, triisopropoxy aluminum or acondensate thereof or aluminum nitrate can be listed, for example.

While the hydrophilic solvent employed for the suspension in theaforementioned case is not particularly restricted, methyl alcohol,ethyl alcohol, isopropyl alcohol, n-propyl alcohol, t-butyl alcohol,n-butyl alcohol, isobutyl alcohol, ethyl cellosolve, butyl cellosolve,propylene glycol monobutyl ether, dipropylene glycol monomethyl ether,propylene glycol monopropyl ether or acetone can be listed, for example.The aforementioned suspension may contain water.

When keeping the pH of the suspension in the acidic range in theaforementioned case, the kept pH is preferably at least 1.0, morepreferably at least 2.0 in particular. Further, this pH is preferablynot more than 5.0, more preferably not more than 4.0 in particular. Thedanger of acceleration of reaction tends to increase if this pH is lessthan 1.0, while the silicon-aluminum coat consisting of the oxide filmelementally containing silicon and/or aluminum tends to beinsufficiently formed if this pH exceeds 5.0.

When keeping the pH of the suspension in the basic range in theaforementioned case, the kept pH is preferably at least 7.0, morepreferably at least 8.0 in particular. Further, this pH is preferablynot more than 14.0, more preferably not more than 10.0 in particular.The silicon-aluminum coat consisting of the oxide film elementallycontaining silicon and/or aluminum tends to be insufficiently formed ifthis pH is less than 7.0, while danger of acceleration of reaction tendsto increase if this pH exceeds 14.0.

When adding the silicon compound and/or the aluminum compound andperforming stirring or kneading in the aforementioned case, thetemperature of the suspension is preferably at least 20° C., morepreferably at least 50° C. in particular. Further, this temperature ispreferably not more than 120° C., particularly preferably not more than80° C. There is a tendency that no desired thickness of thesilicon-aluminum coat is obtained if this temperature is less than 20°C., while there is a tendency that no silicon-aluminum coat is depositedoutside each metal particle if this temperature exceeds 120° C.

When adding the silicon compound and/or the aluminum compound andperforming stirring or kneading in the aforementioned case, the time forstirring or kneading is preferably at least 30 minutes, more preferablyat least 1 hour in particular. Further, this time is preferably not morethan 50 hours, more preferably not more than 20 hours in particular.Deposition of the coat tends to insufficiently occur if this time isless than 30 minutes, while there is a tendency that no furtherdeposition of the coat occurs to result in economic disadvantage if thistime exceeds 50 hours.

Molybdenum-Phosphorus Coat

The color metallic pigment according to the present invention preferablycomprises a molybdenum-phosphorus coat consisting of an oxide filmelementally containing molybdenum and/or phosphorus on the surface ofthe metal particle forming each base particle.

When the molybdenum-phosphorus coat consisting of the oxide filmelementally containing molybdenum and/or phosphorus is formed on thesurface of the metal particle forming each base particle, homogeneousdeposition of the coat formed thereon is facilitated. Themolybdenum-phosphorus coat has corrosion resistance, whereby an effectof preventing abnormal reaction between a treatment solution and themetal particle is also attained in a subsequent step of forming thecoat.

A compound having composition such as MoO₃, Mo₂O₃, MoO, nAl₂O₃.mMoO₃,nAl₂O₃.mMo₂O₃, nAl₂O₃.mMoO, P₂O₅ or nAl₂O₃.mP₂O₅ (n, m: arbitrarypositive real numbers) can be listed as a specific example of thecompound elementally containing molybdenum and/or phosphorus containedin this molybdenum-phosphorus coat.

The elemental quantity of molybdenum and/or phosphorus contained in thismolybdenum-phosphorus coat is preferably varied with the specificsurface area of the metal particle employed as the base particle. Inother words, it can be said preferable to increase the elementalquantity of molybdenum and/or phosphorus with respect to a metalparticle having a large specific surface area and to reduce theelemental quantity of molybdenum and/or phosphorus with respect to themetal particle having a small specific surface area.

In a general case, however, the elemental quantity of molybdenum and/orphosphorus contained in this molybdenum-phosphorus coat is preferably atleast 0.01 parts by mass with respect to 100 parts by mass of the metalparticles forming the base particles, more preferably at least 0.05parts by mass in particular. Further, this quantity is preferably notmore than 5.0 parts by mass, more preferably not more than 2.0 parts bymass in particular. There is a tendency that desired chemical stabilityis hard to obtain if this quantity is less than 0.01 parts by mass,while there is a tendency for such inconvenience that the color tone(i.e., metallic luster) of the color metallic pigment is remarkablylowered, the color metallic pigment flocculates, physical filmproperties such as moisture resistance, adhesiveness and weatherresistance are reduced if this quantity exceeds 5.0 parts by mass.

Molybdenum-Phosphorus Coat Forming Step

While a method of forming the molybdenum-phosphorus coat consisting ofthe oxide film elementally containing molybdenum and/or phosphorus onthe surface of the metal particle forming each base particle of thecolor metallic pigment according to the present invention is notparticularly restricted, a method of adding an aqueous solution preparedby dissolving a molybdenum compound in hydrogen peroxide water and/or aphosphorus compound to a slurried or pasty suspension prepared bysuspending the metal particles in a hydrophilic solvent and performingstirring or kneading thereby forming a hydrated film elementallycontaining molybdenum and/or phosphorus on the surface of each metalparticle and finally performing heat treatment at a high temperature forconverting the hydrated film to an oxide film is preferable, forexample. It is recommended to previously solid-liquid separate the pastecontaining the metal particles each having the hydrated film from theaforementioned suspension before the final heat treatment.

While the molybdenum compound employed in the aforementioned method isnot particularly restricted, polymolybdic peroxide expressed in acomposition formula: Mo_(x)O_(y).mH₂O₂.nH₂O (x denotes an integer of 1or 2, y denotes an integer of 2 to 5 and m and n denote arbitrarypositive real numbers), ammonium molybdate or phosphomolybdic acid canbe listed, for example. Polymolybdic peroxide can be prepared bydissolving metallic molybdenum powder or molybdenum oxide in a hydrogenperoxide solution (concentration: 5 to 40%).

While the phosphorus compound employed in the aforementioned method isnot particularly restricted, orthophosphoric acid, phosphorous acid,hypophosphorous acid, phosphinic acid, pyrophosphoric acid orpolyphosphoric acid can be listed, for example.

While the hydrophilic solvent employed for the suspension in theaforementioned case is not particularly restricted, methyl alcohol,ethyl alcohol, isopropyl alcohol n-propyl alcohol, t-butyl alcohol,n-butyl alcohol, isobutyl alcohol, ethyl cellosolve, butyl cellosolve,propylene glycol monobutyl ether, dipropylene glycol monomethyl ether,propylene glycol monopropyl ether or acetone can be listed, for example.The aforementioned suspension may contain water.

When adding the aqueous solution prepared by dissolving the molybdenumcompound to the hydrogen peroxide water and/or the phosphorus compoundand performing stirring or kneading in the aforementioned case, the pHof the suspension is preferably at least 1.0, more preferably at least2.0 in particular. Further, this pH is preferably not more than 10.0,more preferably not more than 8.0 in particular. The metal particlestend to easily flocculate if this pH is less than 1.0 or in excess of10.0.

Second Coat

The color metallic pigment according to the present invention preferablycomprises a second coat consisting of an oxide film or an oxynitridefilm containing at least one element selected from a group consisting oftitanium, zirconium, zinc, iron, chromium and cerium outside the cobaltcoat.

When the second coat consisting of the oxide film or the oxynitride filmcontaining at least one element among titanium, zirconium, zinc, iron,chromium and cerium is further formed outside the cobalt coat, the colortone of the color metallic pigment can be rendered more multicolored.Among these, an oxide film or an oxynitride film elementally containingtitanium is particularly preferable since an excellent interferencecolor is easy to obtain.

A titanium oxide such as rutile, anatase, TiO, Ti₂O₃ or Ti₃O₅ or atitanium oxynitride can be listed as a specific example of the compoundelementally containing titanium contained in this second coat. Amongthese, the titanium oxide such as rutile, TiO, Ti₂O₃ or Ti₃O₅ or thetitanium oxynitride is particularly preferable.

Rutile-type titanium oxide can be formed at a relatively low temperatureby forming a hydrated film elementally containing titanium on the outersurface of the cobalt coat and heating the same, and hence a second coatcontaining rutile-type titanium oxide can be formed also in the colormetallic pigment employing the metal particle made of a low meltingpoint metal such as aluminum as the base particle.

The thickness of this second coat is preferably at least 0.01 μm, morepreferably at least 0.05 μm in particular. Further, this thickness ispreferably not more than 1 μm, more preferably not more than 0.8 μm inparticular. The color metallic pigment tends to exhibit no desired colorif this thickness is less than 0.01 μm, while the luster of the colormetallic pigment tends to be damaged if this thickness exceeds 1 μm.

The quantity of at least one element selected from the group consistingof titanium, zirconium, zinc, iron, chromium and cerium contained inthis second coat is preferably at least 0.5 parts by mass with respectto 100 parts by mass of the metal particles forming the base particles,more preferably at least 1.0 part by mass in particular. Further, thisquantity is preferably not more than 200 parts by mass, more preferablynot more than 100 parts by mass in particular. There is a tendency thata color metallic pigment having color traveling is hard to obtain ifthis quantity is less than 0.5 parts by mass, while the luster of thecolor metallic pigment tends to lower if this quantity exceeds 200 partsby mass.

Second Coat Forming Step

While a method of forming the second coat consisting of the oxide filmor the oxynitride film containing at least one element selected from thegroup consisting of titanium, zirconium, zinc, iron, chromium and ceriumoutside the cobalt coat of the color metallic pigment according to thepresent invention is not particularly restricted, a method of adding acompound containing at least one element selected from the groupconsisting of titanium, zirconium, zinc, iron, chromium and cerium to aslurried or pasty pH-adjusted suspension prepared by suspending themetal particles each having the cobalt coat in a hydrophilic solvent andhydrolyzing this compound while performing stirring or kneading therebydepositing a hydrolysate of this compound on the outer surface of thecobalt coat provided on the metal particle, forming a hydrated filmcontaining at least one element selected from the group consisting oftitanium, zirconium, zinc, iron, chromium and cerium and finallyperforming heat treatment at a high temperature for converting thehydrated film to an oxide film or an oxynitride film is preferable, forexample. It is recommended to previously solid-liquid separate the pastecontaining the metal particles each having the hydrated film and thecobalt coat from the aforementioned suspension before the final heattreatment.

While the compound elementally containing titanium employed in theaforementioned method is not particularly restricted, titanium alkoxide,a titanium chelate compound, a titanium coupling agent, titanium sulfateor titanium chloride can be listed, for example.

Tetrabutoxy titanium, tetraisopropoxy titanium, tetraethoxy titanium,tetrakis(2-ethylhexoxy) titanium or a condensate thereof, tetrastearoxytitanium, diisopropoxybis(acetylacetonato) titanium,dibutoxybis(triethanolaminato) titanium, dihydroxybis(lactato) titanium,isopropyltri(N-aminoethylaminoethyl) titanate orisopropyltris(dioctylpyrophosphate) titanate can be listed as a specificexample of titanium alkoxide, the titanium chelate compound or thetitanium coupling agent.

Among these compounds elementally containing titanium, tetrabutoxytitanium, tetraisopropoxy titanium, diisopropoxybis(acetylacetonato)titanium, dibutoxybis(triethanolaminato) titanium, dihydroxybis(lactato)titanium and isopropyltri(N-aminoethylaminoethyl) titanate areparticularly preferable.

While the compound elementally containing zirconium, zinc, iron,chromium or cerium employed in the aforementioned method is notparticularly restricted, tetrabutyl zirconate, zirconium acylate,zirconium acetylacetonate, diethoxyzinc, dimethoxyzinc, zinc acetate,ferric nitrate, chromic acid or cerium acetate can be listed, forexample.

While the hydrophilic solvent employed for the suspension in theaforementioned case is not particularly restricted, methyl alcohol,ethyl alcohol, isopropyl alcohol, n-propyl alcohol, t-butyl alcohol,n-butyl alcohol, isobutyl alcohol, ethyl cellosolve, butyl cellosolve,propylene glycol monobutyl ether, dipropylene glycol monomethyl ether,propylene glycol monopropyl ether or acetone can be listed, for example.The aforementioned suspension may contain water.

More specifically, a method of adding the compound containing at leastone element selected from the group consisting of titanium, zirconium,zinc, iron, chromium and cerium while keeping the pH of a slurried orpasty suspension prepared by suspending the metal particles each havingthe cobalt coat in a hydrophilic solvent and hydrolyzing this compoundthereby depositing a hydrolysate of this compound on the outer surfaceof the cobalt coat provided on the metal particle, forming a hydratedfilm containing at least one element selected from the group consistingof titanium, zirconium, zinc, iron, chromium and cerium and finallyperforming heat treatment in the air or in a non-oxidizing atmosphere ata high temperature and converting the hydrated film to an oxide film oran oxynitride film is particularly preferable as a method of forming thesecond coat consisting of the oxide film or the oxynitride filmcontaining at least one element selected from the group consisting oftitanium, zirconium, zinc, iron, chromium and cerium outside the cobaltcoat of the color metallic pigment according to the present invention.

In the aforementioned method, it is recommended to previouslysolid-liquid separate the paste containing the metal particles eachhaving the hydrated film and the cobalt coat from the aforementionedsuspension before the final heat treatment. In the finalhigh-temperature heat treatment, a method of performing heating not inthe air but in the non-oxidizing atmosphere is preferable. When formingnot an oxide film but an oxynitride film, further, a method ofperforming heating in an atmosphere containing ammonia or nitrogen ispreferable.

When adding the compound containing at least one element selected fromthe group consisting of titanium, zirconium, zinc, iron, chromium andcerium and performing stirring or kneading in the aforementioned case,the pH of the suspension is preferably at least 7.0, more preferably atleast 8.0 in particular. Further, this pH is preferably not more than14.0, more preferably not more than 10.0 in particular. The coat tendsto be insufficiently formed if this pH is less than 7.0, while danger ofrunaway of reaction tends to increase if this pH exceeds 14.0.

When adding the compound containing at least one element selected fromthe group consisting of titanium, zirconium, zinc, iron, chromium andcerium and performing stirring or kneading in the aforementioned case,the temperature of the suspension is preferably at least 20° C., morepreferably at least 30° C. in particular. Further, this temperature ispreferably not more than 120° C., particularly preferably not more than100° C. Formation of the coat tends to be insufficient if thistemperature is less than 20° C., while there is a tendency that the coatis not homogeneously deposited outside each metal particle if thistemperature exceeds 120° C.

When adding the compound containing at least one element selected fromthe group consisting of titanium, zirconium, zinc, iron, chromium andcerium and performing stirring or kneading in the aforementioned case,the time for the stirring or kneading is preferably at least 30 minutes,more preferably at least 1 hour in particular. Further, this time ispreferably not more than 50 hours, particularly preferably not more than20 hours. Deposition of the coat tends to insufficiently occur if thistime is less than 30 minutes, while deposition of the coat tends not tofurther progress to result in economic disadvantage if this time exceeds50 hours.

When finally performing heat treatment at a high temperature in theaforementioned case, the temperature for the heat treatment ispreferably at least 250° C., more preferably at least 350° C. inparticular. Further, this temperature is preferably not more than 800°C., particularly preferably not more than 650° C. Color development ofthe color metallic pigment tends to deteriorate if this temperature isless than 250° C., while agglomeration of the color metallic pigmenttends to increase if this temperature exceeds 800° C.

When finally performing heat treatment at a high temperature in theaforementioned case, the time for the heat treatment is preferably atleast 30 minutes, more preferably at least 1 hour in particular. Thistime is preferably not more than 10 hours, particularly preferably notmore than 5 hours. Color development of the color metallic pigment tendsto deteriorate if this time is less than 30 minutes, while there is atendency that the metal particles flocculate or the color tone of thecolor metallic pigment darkens if this time exceeds 10 hours.

Weather-Resistant Coat

When the color metallic pigment according to the present invention hasthe second coat, the color metallic pigment preferably comprises aweather-resistant coat consisting of an oxide film containing at leastone element selected from a group consisting of aluminum, silicon andcerium outside the second coat.

When the color metallic pigment according to the present invention hasthe second coat consisting of the oxide film or the oxynitride filmelementally containing titanium, the color metallic pigment particularlypreferably comprises the weather-resistant coat consisting of the oxidefilm containing at least one element selected from the group consistingof aluminum, silicon and cerium outside the second coat.

When the weather-resistant coat consisting of the oxide film containingat least one element selected from the group consisting of aluminum,silicon and cerium is formed outside the second coat consisting of theoxide film or the oxynitride film elementally containing titanium,photocatalytic activity of a titanium compound such as titanium oxidecan be so reduced that it is possible to prevent a film formed by apaint compounded with the color metallic pigment according to thepresent invention from discoloration for improving weather resistance.

A compound having composition such as Al₂O₃, SiO₂, SiO, CeO₂ or Ce₂O₃can be listed as a specific example of the compound containing at leastone element selected from the group consisting of aluminum, silicon andcerium contained in this weather-resistant coat.

The thickness of this weather-resistant coat is preferably at least 0.01μm, more preferably at least 0.02 μm in particular. Further, thisthickness is preferably not more than 0.5 μm, more preferably not morethan 0.2 μm in particular. There is a tendency that photocatalyticactivity of the titanium compound cannot be sufficiently suppressed ifthis thickness is less than 0.01 μm, while the luster of the colormetallic pigment tends to be damaged if this thickness exceeds 0.5 μm.

The quantity of at least one element selected from the group consistingof aluminum, silicon and cerium contained in this weather-resistant coatis preferably at least 0.01 parts by mass with respect to 100 parts bymass of the metal particles forming the base particles, more preferablyat least 0.1 parts by mass in particular. Further, this quantity ispreferably not more than 5.0 parts by mass, more preferably not morethan 2.0 parts by mass in particular. There is a tendency thatphotocatalytic activity of the titanium compound cannot be sufficientlysuppressed if this quantity is less than 0.01 parts by mass, while theluster of the color metallic pigment tends to lower if this quantityexceeds 5.0 parts by mass.

Weather-Resistant Coat Forming Step

While a method of forming the weather-resistant coat consisting of theoxide film containing at least one element selected from the groupconsisting of aluminum, silicon and cerium outside the second coat ofthe color metallic pigment according to the present invention is notparticularly restricted, a method similar to the aforementionedsilicon-aluminum coat forming step, for example, is preferable as amethod of forming a weather-resistant coat consisting of an oxide filmcontaining at least one element selected from a group consisting ofaluminum and silicon among these methods.

Further, a method of adding a cerium compound to a slurried or pastysuspension prepared by suspending the metal particles each having thecobalt coat and the second coat in a hydrophilic solvent and performingheating/stirring or heating/kneading while keeping the pH of thesuspension basic thereby forming a hydrated film elementally containingcerium on the surface of the second coat provided on the metal particlefor finally performing heat treatment at a high temperature andconverting the hydrated film to an oxide film is preferable as a methodof forming a weather-resistant coat consisting of an oxide filmelementally containing cerium among the aforementioned methods. It isrecommended to previously solid-liquid separate the paste containing themetal particles each having the hydrated film from the aforementionedsuspension before the final heat treatment.

While the cerium compound employed in the aforementioned method is notparticularly restricted, cerium acetate, cerium nitrate or ceriumalkoxide can be listed, for example.

Further, while the hydrophilic solvent employed for the suspension inthe aforementioned case is not particularly restricted, methyl alcohol,ethyl alcohol, isopropyl alcohol, n-propyl alcohol, t-butyl alcohol,n-butyl alcohol, isobutyl alcohol, ethyl cellosolve, butyl cellosolve,propylene glycol monobutyl ether, dipropylene glycol monomethyl ether,propylene glycol monopropyl ether or acetone can be listed. Theaforementioned suspension may contain water.

When performing heating/stirring or heating/kneading with addition ofthe cerium compound in the aforementioned case, the pH of the suspensionis preferably at least 7.0, more preferably at least 8.0 in particular.Further, this pH is preferably not more than 14.0, more preferably notmore than 10.0 in particular. The coat tends to be insufficiently formedif this pH is less than 7.0, while danger of runaway of reaction tendsto increase if this pH exceeds 14.0.

Resin Composition

The resin composition according to the present invention is a resincomposition containing the color metallic pigment according to thepresent invention and resin. Throughout the specification, it is assumedthat the description “resin composition” includes a paint and a filmthereof, ink and a film thereof and a resin composition molding preparedby injection molding or the like.

The color metallic pigment according to the present invention can bepreferably compounded with a resin composition such as a paint or inkalong with binder resin. The resin composition such as a paint or inkcompounded with the color metallic pigment according to the presentinvention may be of any type such as an organic solvent type or aqueouscomposition, or powder coating. The color metallic pigment according tothe present invention is particularly preferably compounded with anaqueous resin composition such as a water-based paint or water-color inkamong these diverse types of resin compositions.

The content of the color metallic pigment according to the presentinvention in the resin composition according to the present invention ispreferably at least 0.1 percent by mass, particularly preferably atleast 1.0 percent by mass. Further, this content is preferably not morethan 30 percent by mass, particularly preferably not more than 20percent by mass. There is a tendency that sufficient metallic effectcannot be obtained if this content is less than 0.1 percent by masswhile bad influence may be exerted on physical properties of the resincomposition such as weather resistance, corrosion resistance andmechanical strength if this content exceeds 30 percent by mass.

While the resin contained in the resin composition according to thepresent invention is not particularly restricted but resin generallyemployed as a binder in a resin composition such as a paint or ink canbe preferably employed, acrylic resin, alkyd resin, polyester resin,polyurethane resin, polyvinyl acetate resin, nitrocellulose resin orfluorocarbon resin can be listed, for example.

The resin composition according to the present invention may containwater, an organic solvent or the like.

Further, the resin composition according to the present invention maycontain a pigment or an additive at need in a range not damaging thecharacteristics of the resin composition according to the presentinvention, in addition to the color metallic pigment according to thepresent invention and the resin.

While the pigment compoundable with the resin composition according tothe present invention is not particularly restricted, phthalocyanine,quinacridone, isoindolinone, perylene, azo lake, iron oxide, chromeyellow, carbon black, titanium oxide, pearl mica, other extenderpigments, a color pigment or a dye can be listed, for example.

While the additive compoundable with the resin composition according tothe present invention is not particularly restricted, a surface activeagent, a hardener, an ultraviolet absorber, a static eliminator or athickener can be listed, for example.

While the material of a base for applying the resin compositionaccording to the present invention as a paint or ink is not particularlyrestricted, a base consisting of paper, wood, fabric, plastic or metal,can be listed, for example. The resin composition according to thepresent invention can be preferably applied to any base by properlyselecting the type and the composition of the binder resin compoundedwith the resin composition.

When employing the resin composition according to the present inventionas a paint or ink, the resin composition may be directly applied to thebase, while the base may be provided with an undercoating layer or anintermediate layer by electrodeposition coating or the like on asubstrate for applying the resin composition thereto.

When employing the resin composition according to the present inventionis employed as a paint or ink, a film consisting of the resincomposition according to the present invention may form the outermostlayer, while a topcoat layer may be formed on the film consisting of theresin composition according to the present invention.

While the present invention is now described in more detail withreference to Examples, the present invention is not restricted to these.

EXAMPLE 1

First, a solution obtained by adding 0.3 g of metallic molybdenum powderto 3 g of hydrogen peroxide water containing 30% (w/v) of hydrogenperoxide piecemeal and making reaction was dissolved in 200 g ofisopropyl alcohol (hereinafter abbreviated as IPA), and 40 g (30 g asaluminum content) of commercially available aluminum particles (5422NSby Toyo Aluminum K.K., solid content: 75% (w/w), average particlediameter: 19 μm, average thickness: 1 μm) were further added to thesolution for preparing slurry, which in turn was stirred/mixed at 75° C.for 1 hour.

Thereafter monoethanolamine was added to the aforementioned slurry, foradjusting the pH value of the slurry to 10.0. 15 g of cobalt acetate(II) tetrahydrate was dissolved in 40 g of water and added to thepH-adjusted slurry, which in turn was further stirred/mixed at 75° C.for 2 hours.

After completion of reaction, the slurry was solid-liquid separatedthrough a filter, and the obtained aluminum pigment (hardly colored) washeat-treated in the air at 500° C. for 3 hours. The heat-treatedaluminum pigment presented yellow-green, and had excellent metalliceffect.

EXAMPLE 2

12 g of tetrabutoxy titanium, 0.5 g of monoethanolamine and 10 g ofwater were added to slurry prepared by dispersing 30 g of the aluminumpigment obtained in Example 1 in 200 g of IPA, and stirred/mixed at 75°C. for 2 hours for making reaction.

After completion of the reaction, the slurry was solid-liquid separatedthrough a filter, and the obtained aluminum pigment was heat-treated inan argon atmosphere at 600° C. for 3 hours. The heat-treated aluminumpigment presented an appearance varying from pink to gold with the angleof observation, and had excellent metallic effect.

EXAMPLE 3

0.3 g of phosphoric acid (active ingredient: 98% (w/w)) was dissolved in200 g of isopropyl alcohol (hereinafter abbreviated as IPA), 40 g (30 gas aluminum content) of commercially available aluminum particles(5422NS by Toyo Aluminum K.K.) and ethylenediamine were added foradjusting the pH value of the slurry to 10.0, and the slurry wasstirred/mixed at 75° C. for 1 hour.

Thereafter 10 g of cobalt nitrate (II) hexahydrate was dissolved in 40 gof IPA and added to the aforementioned slurry, which in turn was furtherstirred/mixed at 75° C. for 2 hours.

After completion of reaction, the slurry was solid-liquid separatedthrough a filter, and the obtained aluminum pigment (hardly colored) washeat-treated in the air at 300° C. for 3 hours. The heat-treatedaluminum pigment presented pale yellow, and had excellent metalliceffect.

EXAMPLE 4

12 g of tetraisopropoxy titanium, 1.5 g ofdibutoxybis(triethanolaminato) titanium and 10 g of water were added toslurry prepared by dispersing 30 g of the aluminum pigment obtained inExample 3 in 200 g of IPA, and stirred/mixed at 75° C. for 2 hours formaking reaction.

After completion of the reaction, the slurry was solid-liquid separatedthrough a filter, and the obtained aluminum pigment was heat-treated inan argon atmosphere at 600° C. for 3 hours. The heat-treated aluminumpigment presented an appearance varying from blue to purple with theangle of observation, and had excellent metallic effect.

EXAMPLE 5

0.6 g of phosphomolybdic acid was dissolved in 200 g of dipropyleneglycol monomethyl ether, 40 g (30 g as aluminum content) of commerciallyavailable aluminum particles (5422NS by Toyo Aluminum K.K.) were addedthereto, and stirred/mixed at 90° C. for 1 hour.

Thereafter γ-aminopropyl triethoxysilane was added to the aforementionedslurry, for adjusting the pH value of the slurry to 9.5.

30 g of cobalt oxalate (II) dihydrate was dissolved in 40 g of water andadded to the pH-adjusted slurry, which in turn was further stirred/mixedat 90° C. for 2 hours. After completion of reaction, the slurry wassolid-liquid separated through a filter, and the obtained aluminumpigment (hardly colored) was heat-treated in the air at 300° C. for 3hours. The heat-treated aluminum pigment presented green, and hadexcellent metallic effect.

EXAMPLE 6

18 g of tetrabutoxy titanium and 3 g of a 10% (w/v) ammonia aqueoussolution were added to slurry prepared by dispersing 30 g of thealuminum pigment obtained in Example 5 in 200 g of ethyl alcohol, andstirred/mixed at 75° C. for 2 hours for making reaction.

After completion of the reaction, the slurry was solid-liquid separatedthrough a filter, and the obtained aluminum pigment was heat-treated innitrogen at 600° C. for 3 hours. The heat-treated aluminum pigmentpresented an appearance varying from green to brown with the angle ofobservation, and had excellent metallic effect.

EXAMPLE 7

Polyphosphoric acid was dissolved in 200 g of isopropyl alcohol, 40 g(30 g as aluminum content) of commercially available aluminum particles(5422NS by Toyo Aluminum K.K.) were added and stirred/mixed at 50° C.for 1 hour. Thereafter monoethanolamine was added to the aforementionedslurry for adjusting the pH value of the slurry to 8.5.

40 g of triisopropoxy aluminum (hereinafter abbreviated as TEOS) wasadded to the pH-adjusted slurry, which in turn was further stirred/mixedat 50° C. for 10 hours. In the course of this process, the pH value ofthe slurry was checked every 2 hours, and the pH value was adjusted to8.5 by adding monoethanolamine.

Thereafter 5 g of cobalt acetate (II) tetrahydrate was added to theslurry, which in turn was stirred/mixed at 75° C. for 2 hours. Aftercompletion of reaction, the slurry was solid-liquid separated through afilter, and the obtained aluminum pigment was heat-treated in nitrogenat 300° C. for 3 hours. The heat-treated aluminum pigment presentedbeige, and had excellent metallic effect.

EXAMPLE 8

30 g of tetrabutoxy titanium, 3 g of triethanolamine and 15 g of waterwere added to slurry obtained by dispersing 30 g of the aluminum pigmentobtained in Example 7 in 200 g of IPA, and stirred/mixed at 75° C. for 2hours, for making reaction.

After completion of the reaction, the slurry was solid-liquid separatedthrough a filter, and the obtained aluminum pigment was heat-treated inthe air at 500° C. for 3 hours. The heat-treated aluminum pigmentpresented an appearance varying from pale green to pink with the angleof observation, and had excellent metallic effect.

EXAMPLE 9

5 g of tetraethoxysilane and 15 g of a 10% (w/v) ammonia aqueoussolution were added to slurry prepared by dispersing 30 g of thealuminum pigment obtained in Example 8 in 200 g of IPA, andstirred/mixed at 75° C. for 5 hours, for making reaction.

After completion of the reaction, the slurry was solid-liquid separatedthrough a filter, and the obtained aluminum pigment was heat-treated ina nitrogen atmosphere at 600° C. for 3 hours. The heat-treated aluminumpigment presented an appearance varying from pale green to pink with theangle of observation, and had excellent metallic effect.

EXAMPLE 10

4.5 g of aluminum nitrate and 15 g of a 10% (w/v) ammonia aqueoussolution were added to slurry prepared by dispersing 30 g of thealuminum pigment obtained in Example 8 in 200 g of water, andstirred/mixed at 75° C. for 5 hours, for making reaction.

After completion of the reaction, the slurry was solid-liquid separatedthrough a filter, and the obtained aluminum pigment was heat-treated inan argon atmosphere at 600° C. for 3 hours. The heat-treated aluminumpigment presented an appearance varying from pale green to pink with theangle of observation, and had excellent metallic effect.

EXAMPLE 11

5 g of cerium acetate (III) monohydrate and 15 g of a 10% (w/v) ammoniaaqueous solution were added to slurry prepared by dispersing 30 g of thealuminum pigment obtained in Example 8 in 200 g of water, andstirred/mixed at 75° C. for 5 hours, for making reaction.

After completion of the reaction, the slurry was solid-liquid separatedthrough a filter, and the obtained aluminum pigment was heat-treated inthe air at 550° C. for 3 hours. The heat-treated aluminum pigmentpresented an appearance varying from pale green to pink with the angleof observation, and had excellent metallic effect.

EXAMPLE 12

40 g (30 g as aluminum content) of commercially available aluminumparticles (5422NS by Toyo Aluminum K.K.) and monoethanolamine were addedto 200 g of dipropylene glycol monomethyl ether for adjusting the pHvalue of slurry to 10.0.

15 g of cobalt acetate (II) tetrahydrate was dissolved in 40 g of waterand added to the pH-adjusted slurry, which in turn was furtherstirred/mixed at 75° C. for 2 hours. In the course of this process, thealuminum particles reacted in the slurry and generated a large quantityof hydrogen gas, to finally provide brown slurry.

After completion of the reaction, the slurry was solid-liquid separatedthrough a filter, 30 g of tetrabutoxy titanium, 3 g of triethanolamineand 15 g of water were added to slurry prepared by re-dispersing theobtained aluminum pigment in 200 g of IPA, and stirred/mixed at 75° C.for 2 hours, for making reaction.

After completion of the reaction, the slurry was solid-liquid separatedthrough a filter, and the obtained aluminum pigment was heat-treated innitrogen at 600° C. for 3 hours. The heat-treated aluminum pigmentpresented an appearance varying from red to orange with the angle ofobservation, and had excellent metallic effect.

Comparative Example 1

15 g of tetrabutoxy titanium was added to slurry prepared by dispersing30 g of aluminum particles prepared by cleaning commercially availablealuminum particles (5422NS by Toyo Aluminum K.K.) with acetone,thereafter sucking/filtrating the same and drying the same at 50° C. for2 hours in 300 g of n-butanol, and a solution prepared by dissolving 7.5g of water in 50 g of n-butanol was gradually added thereto for makingreaction at 75° C. for 1 hour.

After completion of the reaction, the slurry was solid-liquid separatedthrough a filter, and the obtained aluminum pigment was heat-treated inthe air at 250° C. for 15 minutes. The heat-treated aluminum pigment wassilver and hardly colored. Coarse particles of an aggregate resultingfrom reaction between water and aluminum were mixed into powdercontaining the heat-treated aluminum.

Comparative Example 2

60 g of cobalt nitrate (II) hexahydrate, 30 g of oxalic acid and 45 g ofiron-EDTA-chelate were dissolved in 1000 g of water, and 120 g oftriethanolamine and a 1N sodium hydroxide solution were added forpreparing a solution adjusted to 7.3 in pH value.

While 30 g of aluminum particles prepared by cleaning commerciallyavailable aluminum particles (5422NS by Toyo Aluminum K.K.) withacetone, thereafter sucking/filtrating the same and drying the same at50° C. for 2 hours and 500 g of ethanol were added to this solution,which in turn was heated at 85° C. for 10 minutes, generation ofhydrogen gas resulting from reaction between the treatment solution andthe aluminum pigment was recognized during the treatment.

5000 g of water was added to this slurry, which in turn was thereaftersolid-liquid separated through a filter. While beige powder was mixedinto the obtained aluminum pigment, the aluminum pigment itself washardly colored. A large aggregate resulting from reaction between waterand aluminum was mixed into powder containing the aluminum pigment.

Comparative Example 3

120 g of water and 10 g of a 25% (w/v) ammonia aqueous solution wereadded to slurry prepared by dispersing 30 g of aluminum particlesprepared by cleaning commercially available aluminum particles (5422NSby Toyo Aluminum K.K.) with acetone, thereafter sucking/filtrating thesame and drying the same at 50° C. for 2 hours in 300 g of IPA, andheated to 60° C.

Thereafter a solution prepared by dissolving 90 g of tetraethoxysilanein 120 g of IPA was gradually added for 3 hours, and thereafter reactedat 55° C. for 14 hours. During the treatment step, the aluminumparticles reacted with the treatment solution, to generate a largequantity of hydrogen gas. After completion of the reaction, the slurrywas solid-liquid separated through a filter, and the obtained aluminumpigment was dried in the air at 80° C. for 3 hours.

While a large aggregate resulting from reaction of water and aluminumwas mixed into powder containing the heat-treated aluminum pigment, thiswas passed through a sieve of 45 μm, and 20 g of obtained powder wasre-dispersed in 200 g of IPA. 10 g of tetrabutoxy titanium, 2 g oftriethanolamine and 10 g of water were added to this slurry, which inturn was stirred/mixed at 75° C. for 2 hours, for making reaction.

After completion of the reaction, the slurry was solid-liquid separatedthrough a filter, and the obtained aluminum pigment was heat-treated innitrogen at 600° C. for 3 hours. While the heat-treated aluminum pigmentpresented an appearance varying from beige to orange with the angle ofobservation, this was an aluminum pigment having less metallic effectwith a large quantity of aggregates.

Preparation of Water-Based Metallic Base Paint

Each of the aluminum pigments obtained in Examples 1 to 12 andcomparative examples 1 to 3 was used for preparing a water-basedmetallic base paint in the following composition. The finallyheat-treated aluminum pigment was employed as the aluminum pigment.Aluminum pigments passed through a sieve of 45 μm in pore size were usedas the aluminum pigments obtained in comparative examples 1 to 3.[Composition of Water-Based Metallic Base Paint] water-soluble acrylicresin (*1) 28.2 g melamine resin (*2) 4.4 g triethanolamine 1.1 gdeionized water 44.8 g isopropyl alcohol 3.0 g aluminum pigment (*3) 3.0g as solid content

In the aforementioned composition, it is assumed that the respectivesymbols denote the following substances:

-   -   1: Armatex WA911 by Mitsui Chemicals    -   2: Cymel 350 by Mitsui Chemicals    -   3: aluminum pigments obtained in Examples 1 to 12 or comparative        examples 1 to 3

Preparation of Painted Plate

Each of the aforementioned water-based metallic base paints preparedwith the aluminum pigments obtained in Examples 1 to 12 or comparativeexamples 1 to 3 was applied to a test steel plate previouslyelectrodeposition-coated with a primary rust prevention paint by airspraying so that the thickness of the dried film was 13 μm, and thesteel plate was predried at 90° C. for 10 minutes, coated with anorganic solvent-type topcoat paint having the following composition byair spraying so that the thickness of the dried film was 40 μm and driedat 130° C. for 30 minutes, thereby preparing a metallic painted plate.[Composition of Organic Solvent-Type Topcoat Paint] acrylic resin (*1)140 g  melamine resin (*2) 50 g Solvesso 100 60 g

In the aforementioned composition, it is assumed that the respectivesymbols denote the following substances:

-   -   1: Armatex 110 by Mitsui Chemicals    -   2: Uban 20SE60 by Mitsui Chemicals

Performance Evaluation

As to the metallic painted plates containing the aluminum pigmentsobtained according to Examples 1 to 12 or comparative examples 1 to 3 asdescribed above in the film, items of appearance, hue, chroma, colortraveling (property of the hue varying with the angle of observation)and metallic effect of the film of each painted plate were evaluatedaccording to the following evaluation methods. Table 1 shows theobtained results of evaluation.

(i) Method of Evaluating Appearance of Film

The appearance of the film of the metallic painted plate was visuallyobserved and evaluated according to the following criteria ofevaluation:

-   -   5: surface extremely smooth    -   4: surface smooth    -   3: surface waved but lustered    -   2: surface finely irregular    -   1: surface grained

(ii) Method of Evaluating Hue of Film

The hue of the film of the metallic painted plate was visually observedwhile varying the angle of observation, for evaluating the observedcolor or the way of variation of the color.

(iii) Method of Evaluating Chroma of Film

The chroma of the film of the metallic painted plate was evaluatedaccording to the following criteria of evaluation by measuring the cvalue (=(a²+b²)^(1/2)) with a differential calorimeter (SM-6-CH by SugaTest Instruments Co., Ltd.):

-   -   5: 20≦c    -   4: 15≦c<20    -   3: 10≦c<15    -   2: 5≦c<10    -   1: c<5

(iv) Method of Evaluating Color Traveling of Film

The appearance of the film of the metallic painted plate was visuallyobserved and evaluated according to the following criteria ofevaluation:

-   -   5: hues of colors in the direction of specular reflection and        the direction of diffuse reflection remarkably varied    -   4: hues of colors in the direction of specular reflection and        the direction of diffuse reflection varied in the same system    -   3: hues of colors in the direction of specular reflection and        the direction of diffuse reflection remained similar with        variation of brightness    -   2: colors in the direction of specular reflection and the        direction of diffuse reflection slightly varied in hue or        brightness    -   1: colors in the direction of specular reflection and the        direction of diffuse reflection hardly varied

(v) Method of Evaluating Metallic Effect of Film

The appearance of the film of the metallic painted plate was visuallyobserved and evaluated according to the following criteria ofevaluation:

-   -   5: exhibited metallic effect equivalent to that in a case of        employing untreated aluminum particles    -   4: exhibited metallic effect, though slightly inferior to that        in the case of employing untreated aluminum particles    -   3: passably exhibited metallic effect, though considerably        inferior to that in the case of employing untreated aluminum        particles    -   2: metallic effect remarkably lowered as compared with that in        the case of employing untreated aluminum particles    -   1: hardly exhibited metallic effect

(vi) Method of Evaluating Weather Resistance of Film

The metallic painted plate was subjected to ultraviolet irradiation for1000 hours with a QUV acceleration weather meter (QUV/SE by Q-PanelCompany) and variation of color difference before and after the test wasmeasured with a differential calorimeter (SM-6-CH by Suga TestInstruments Co., Ltd.) thereby evaluating the weather resistance of thefilm. It can be said that a film having smaller variation of colordifference has superior weather resistance. TABLE 1 Results ofPerformance Evaluation of Films Containing Various Types of AluminumPigments Type of Results of Evaluation Aluminum Color Variation of ColorPigment Appearance Hue Chroma Traveling Metallic Effect DifferenceExample 1 5 yellow-green 4 2 5 0.3 Example 2 4 pink to gold 4 5 5 0.6Example 3 5 pale yellow 3 2 5 0.2 Example 4 4 blue to purple 5 5 4 0.5Example 5 5 green 5 2 5 0.3 Example 6 4 green to brown 5 4 4 0.6 Example7 4 beige 3 3 5 0.2 Example 8 4 pale green to pink 4 5 5 0.7 Example 9 4pale green to pink 4 5 4 0.3 Example 10 4 pale green to pink 4 5 4 0.2Example 11 4 pale green to pink 4 5 4 0.1 Example 12 4 red to orange 5 54 0.7 Comparative 1 uncolored 1 1 3 3.5 Example 1 Comparative 1uncolored 2 1 1 1.5 Example 2 Comparative 1 beige to orange 2 3 2 3.1Example 3

It is understood from the results shown in Table 1 that the films of themetallic painted plates employing the aluminum pigments obtainedaccording to Examples 1 to 12 of the present invention are remarkablysuperior in the items of appearance, hue, color traveling, metalliceffect and weather resistance of the films as compared with the films ofthe metallic painted plates employing the aluminum pigments obtainedaccording to comparative examples 1 to 3.

It is also understood from the results shown in Table 1 that the filmsof the metallic painted plates employing the aluminum pigments obtainedaccording to Examples 1 to 12 of the present invention are colored indiverse hues including colors having hues varying with the angles ofobservation.

The embodiment and Examples disclosed this time must be considered asillustrative in all points and not restrictive. The scope of the presentinvention is shown not by the above description but by the scope ofclaim for patent, and it is intended that all modifications within themeaning and range equivalent to the scope of claim for patent areincluded.

INDUSTRIAL AVAILABILITY

It can be said from the aforementioned results that the color metallicpigment according to the present invention is a color metallic pigmentcapable of implementing colors of diverse hues including a color havinga hue varied with the angle of observation, excellent in finishedappearance, chroma, color traveling, metallic effect and weatherresistance, and manufacturable by a safe and simple manufacturingmethod.

It can also be said that the resin composition according to the presentinvention, containing the color metallic pigment according to thepresent invention and resin, is a resin composition capable ofimplementing colors of diverse hues including a color having a huevaried with the angle of observation, excellent in finished appearance,chroma, color traveling, metallic effect and weather resistance, andmanufacturable by a safe and simple manufacturing method.

1-11. (canceled)
 12. A color metallic pigment comprising metal particlesand a single-layer or multilayer coat covering the surface of each saidmetal particle, comprising a molybdenum-phosphorus coat consisting of anoxide film elementally containing molybdenum and/or phosphorus on thesurface of each said metal particle, wherein at least one layer of saidsingle-layer or multilayer coat is a cobalt coat consisting of ananhydrous oxide film elementally containing cobalt.
 13. The colormetallic pigment according to claim 12, comprising a silicon-aluminumcoat consisting of an oxide film elementally containing silicon and/oraluminum inside said cobalt coat.
 14. The color metallic pigmentaccording to claim 12, comprising a second coat consisting of an oxidefilm or an oxynitride film containing at least one element selected froma group consisting of titanium, zirconium, zinc, iron, chromium andcerium outside said cobalt coat.
 15. The color metallic pigmentaccording to claim 14, wherein said second coat consists of an oxidefilm or an oxynitride film elementally containing titanium.
 16. Thecolor metallic pigment according to claim 15, comprising aweather-resistant coat consisting of an oxide film containing at leastone element selected from a group consisting of aluminum, silicon andcerium outside said second coat.
 17. A resin composition containing thecolor metallic pigment according to claim 12 and resin.
 18. The colormetallic pigment according to claim 12, wherein said cobalt coatmaterially contains a compound having at least one composition selectedfrom a group consisting of CoO, Co₂O₃, Co₃O₄, nCoO.mAl₂O₃ andnCoO.mSiO₂, and said m and said n are positive numbers.
 19. The colormetallic pigment according to claim 12, wherein the quantity of thecobalt element contained in said cobalt coat is in the range of 0.5 to50 parts by mass with respect to 100 parts by mass of said metalparticles.
 20. The color metallic pigment according to claim 12, whereinsaid molybdenum-phosphorus coat materially contains a compound having atleast one composition selected from a group consisting of MoO₃, Mo₂O₃,MoO, nAl₂O₃.mMoO₃, nAl₂O₃.mMo₂O₃, nAl₂O₃.mMoO, P₂O₅ and nAl₂O₃.mP₂O₅,and said m and said n are positive real numbers.
 21. The color metallicpigment according to claim 12, wherein the elemental quantity ofmolybdenum and/or phosphorus contained in said molybdenum-phosphoruscoat is in the range of 0.01 to 5.0 parts by mass with respect to 100parts by mass of said metal particles.